I think this was very creative and I like the art!
If you are going to add more slimes later, like SPEED mentioned below maybe you can use the mouse to click which slime you want to summon from a menu, or maybe hold shift and a menu comes up where you can use wasd or the arrows to select the slime to summon. But with 4 slimes I think the way it is now is good!
I had a lot of fun playing with the slimes!